The muffler for portable working tools is usually directly mounted to the cylinder's exhaust gas outlet as compactly as possible. For these tools there is a very strong demand for a low total weight and small size. This leads to a demand for a small and light muffler, which at the same time gives a satisfactory silencing function. It is also important that the user does not get injured if he comes into contact with the tool's muffler or its exhaust gases. Furthermore, it is obviously important that the exhaust gases do not set fire to adjacent objects, for example grass or twigs in the case of a chain saw. This has lead to the existence of special legal requirements concerning the muffler's surface contact temperature and the exhaust gas temperature in the vicinity. The working tool is usually supplied with a cooling fan and various safety covers around the cylinder and partly around the muffler. It is desirable to achieve a good mix of the exhaust gases in the cooling-air to reduce the temperature. However, in reality this is hard to achieve due to lack of space and with regard to weight.